LottieAnimationView layout stuck in infinite loop

[via-guy]

Which Version of Lottie are you using?

Lottie 4.3.0

Expected Behavior

App does not get stuck

Actual Behavior

App is stuck in an infinite loop.
There was a bug introduced in commit ecdadec where the function layoutAnimation in Sources/Public/Animation/LottieAnimationView.swift calls setNeedsLayout from within a layout function. This causes the layout function to be called again on the next runloop, and again and again repeatedly, causing the UI thread to freeze. I believe removing this line will fix the issue.

[calda]

Can you share a sample project that demonstrates this issue?

[via-guy]

@calda https://github.com/via-guy/LottieDemo

[via-guy]

There seems to be an issue when you have a container view for it.

let animationView = LottieAnimationView(name: "loader")
containerView.addSubview(animationView)
animationView.translatesAutoresizingMaskIntoConstraints = false
containerView.addConstraints(NSLayoutConstraint.constraints(
    withVisualFormat: "V:|-(0)-[contentView]-(0)-|",
    options: NSLayoutConstraint.FormatOptions.alignAllLastBaseline,
    metrics: nil,
    views: ["contentView": animationView]
))
containerView.addConstraints(NSLayoutConstraint.constraints(
    withVisualFormat: "H:|-(0)-[contentView]-(0)-|",
    options: NSLayoutConstraint.FormatOptions.alignAllLastBaseline,
    metrics: nil,
    views: ["contentView": animationView]
))
animationView.backgroundBehavior = .pauseAndRestore
animationView.viewportFrame = animationView.bounds
animationView.loopMode = .loop
animationView.play()

[calda]

This appears to be because you're setting animationView.viewportFrame = animationView.bounds.

I don't think that line is necessary -- if I remove it, your demo runs correctly.

However, this infinite loop happens any time viewportFrame is non-nil, so is definitely a regression we should fix.

[calda]

Here's a fix: #2316